HVAC heat transfer fluid recycling

ABSTRACT

In an HVAC system, an apparatus and method cleanses glycol-containing heat transfer fluid from the HVAC system in a batch process. Heat transfer liquid is admitted to the apparatus from a low pressure side of the system. The heat transfer fluid is filtered in a batch process and returned to a high pressure side of the HVAC system.

This is a continuation of application Ser. No. 08/334,436, filed Nov. 3,1994, which is now U.S. Pat. No. 5,429,753 and a continuation of Ser.No. 08/031,099 filed Mar. 11, 1993, which is now abandoned andapplication(s) are incorporated herein by reference.

FIELD OF THE INVENTION

This invention pertains to heat transfer fluid recycling. Moreparticularly this invention pertains to an apparatus and method forcleaning heat transfer fluid in an HVAC system.

DESCRIPTION OF THE PRIOR ART

Heating, ventilating and air conditioning (HVAC) systems commonlyutilize closed loop systems for pumping heat transfer fluid throughout abuilding. In such a closed loop system, a central air conditioner orboiler forces heat transfer fluid through piping which is then returnedto the air conditioner/boiler. In such systems, glycol is a primarycomponent of the fluid.

After continued use, the heat transfer fluid becomes contaminated withparticulate matter or other contaminants. Also, the glycol can breakdown losing its usefulness and presenting a maintenance hazard to thepipes. As a result, it has become necessary to add glycol to a systemand, from time to time, to clean the heat transfer fluid containedwithin the HVAC system. By cleansing the heat transfer fluid, corrosionand related maintenance problems can be reduced. Also, a clean HVACsystem reduces a danger of biological contamination and may even cutpower costs.

In industrial applications (e.g., a school), an HVAC system may containas much as 10,000 gallons of heat transfer fluid. Prior art techniquesfor cleansing a heat transfer fluid within a system would include simplyremoving the old heat transfer fluid and disposing it. New heat transferfluid is then substituted into the system. However, such disposal isenvironmentally unacceptable. Alternatively, the heat transfer fluid canbe drained from the system and cleansed. However, due to the largevolume of heat transfer fluid in an HVAC system, this procedure is notcommonly practical. Also, if the system is drained, air pockets canresult in the piping when fluid is re-admitted.

It is an object of the present invention to provide an apparatus andmethod for cleansing glycol containing heat transfer fluid within anHVAC system without interruption of the systems normal operation.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a methodand apparatus for cleansing heat transfer fluid in an HVAC system isdisclosed. The method includes drawing off a portion of heat transferfluid from a low pressure side of the HVAC system. The drawn off portionis then cleansed in a batch process. The cleansed portion is thenadmitted under pressure to a high pressure side of the HVAC system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, exploded and partially cut-away view showing anapparatus according to the present invention;

FIG. 2 is a perspective view of a bottom rear of the apparatus of FIG.1;

FIG. 3 is a schematic view of a prior art HVAC system;

FIG. 4 is the view of FIG. 3 with an apparatus of the present inventionincluded;

FIG. 5 is a schematic view showing the apparatus of the presentinvention;

FIG. 6 is a schematic view of control circuitry for use with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the several drawing figures in which identical elementsare number identically throughout, a description of the preferredembodiment will now be provided.

With initial reference to FIG. 3, a prior art HVAC system 10 isschematically shown. The system 10 includes a main HVAC pump 12. Thesystem 10 also includes a heat transfer unit 14 which may be heattransfer coils, heating and cooling loops or the like.

In a commercial environment, the heat transfer unit 14 may bedistributed throughout a building with the pump 12 centrally positionedin a boiler room or the like. A supply conduit 16 connects an outlet ofthe pump 12 with an inlet of the heat transfer unit 14. A return conduit18 connects an outlet of the heat transfer unit 14 with an inlet of thepump 12.

As shown, the HVAC system 10 is a closed loop system. In such systems, aheat transfer fluid containing glycol is pumped from the pump 12 throughsupply conduit 16 to the heat transfer unit 14. After the heat transfer,the heat transfer fluid is then returned to the HVAC pump 12 through thereturn line 18. The pressure of the fluid within the supply conduit 16is at a first pressure P₁ greater than a pressure P₂ of fluid within thereturn conduit 18. P₂ is greater than ambient atmospheric pressure.

The present invention includes a cleaning apparatus 20 installed asschematically shown in FIG. 4. An outlet conduit 22 connects theapparatus 20 to the supply conduit 16. An inlet conduit 24 connects theapparatus 20 to the return conduit 18.

To connect conduits 22,24 to conduits 16,18, any suitable valves can beplaced within conduits 16,18. Preferably, such valves will includecouplings for attaching conduits 22,24 as well as having shut-off valvesfor permitting conduits 22,24 to be decoupled from the system 10 whilepermitting fluid flow through conduits 16,18 when the apparatus 20 isnot in use.

With attention now to FIG. 1, the apparatus 20 includes a housing 26having a rear wall 28, a right wall 29 and a left wall 30. Extendingbetween walls 29,30 (and lapproximately half way through the depth ofthe walls 29,30) is a transverse intermediate wall 31 parallel to wall28. A dividing wall 32 extends between walls 31 and 28. A first base 33extends from a bottom portion of walls 31,32 and joins walls 28,29, and30. The walls 28-33 cooperate to define a first tank 34 and a secondtank 36 each of approximately equal volume and each open to atmosphereat their upper ends.

The housing 26 also includes a second or lower base 38 extending betweenwalls 29,30 on which various hardware will be mounted as will bedescribed. Casters 40 are secured to the lower portion of the housing 26to permit the housing 26 to be moved between locations as desired.

Preferably, the dimensions of the housing 26 are selected such that thehousing 26 may pass through common sized door openings which aretypically two and a half to three feet wide in commercial installations.A handle 42 is secured to the housing 26 to permit an operator to graspthe unit 20 and move it about on casters 40. In FIG. 1, due to thepartial breakaway of wall 29, only handle 42 is shown attached to wall30. It will be appreciated that an additional handle will be attached towall 29 such that an operator may grasp the unit in two locations forease of movement.

As shown in FIG. 1, the walls 30,29 extend forward from intermediatewall 31. A dividing bar 44 extends between walls 30,29. A mounting plate46 is secured to dividing bar 44. The mounting plate 46 receives andretains various components as will be more fully described.

With reference to FIG. 2, the lower back of the unit 20 is shown.Exposed through an opening 28a of wall 28, are an inlet coupling 50 andan outlet coupling 52. Couplings 50,52 may be releasably connected toconduits 24,22 (FIG. 4), respectively. Also exposed through opening 28ais a dirty fluid valve outlet 54 and a clean fluid outlet valve 56 fordraining tanks 34,36, respectively.

With reference back to FIG. 1, a first elbow coupling 58 is providedadjacent an upper end of first tank 34. As a result, fluid admitted tothe coupling 58 is discharged into the interior of tank 34 at its upperend. Similarly, a second elbow coupling 60 is provided near an upper endof tank 36 to discharge fluid into an upper end of tank 36.

Hosing 62 connects first elbow coupling 58 to inlet coupling 50. Hosing64 connects coupling 60 to an outlet of an ultra-filtration filter 72 aswill be more fully described.

The hardware of the apparatus 20 includes a first pump 66 and a secondpump 68. The apparatus further includes a first filter 70 and a secondfilter 72. The first filter 70 is preferably a five micron filter forfiltering out particulate material and coagulated glycol. Second filter72 is preferably an ultra-filtration filter for cleansing glycol. Use offilters including ultra-filtration filters for cleaning glycol heattransfer fluids is shown in commonly assigned U.S. Pat. No. 5,091,081.

A conduit 74 connects an outlet drain 76 (see FIG. 5) on the bottom oftank 34 to an inlet of first pump 66. A conduit 76 connects an outlet ofpump 66 to an inlet of first filter 70. A conduit 78 (FIG. 5) connectsan outlet of first filter 70 with an inlet of the ultra-filtrationfilter 72. Conduit 64 connects a permeate side output ofultra-filtration filter 72 with an inlet at the upper end of tank 36. Aconduit 80 connects an outlet drain 81 at the bottom of tank 36 with aninlet of second pump 68. Finally, a conduit 82 provided with a checkvalve 300 (FIG. 5) connects the outlet of pump 68 with outlet coupling52.

Ultra-filtration filter 72, as is common, includes a condensate outletand a permeate outlet. The permeate outlet is connected via conduit 64to tank 36 such that fluid cleansed by ultra-filtration filter 72 issent to tank 36. The condensate outlet of ultra-filtration filter 72 isconnected via a hosing 84 to a lower inlet 86 (FIG. 5) of tank 34.

Preferably, pump 66 is a positive displacement pump with sufficientpower to force dirty HVAC heat transfer fluid through filters 70,72. Apump 66 having a maximum output pressure of 40 psig is preferred. Pump68 must achieve an output pressure greater than P₁ in conduit 16 (FIG.4). Presently, a pressure of 75 psig is preferred for the maximum outputof pump 68.

As shown in FIG. 1, manual shutoff valves 88,90 are provided on conduits76,84 for shutting off flow through the conduits 76,84. Further, firstand second solenoid actuated flow control valves 92,93 are provided tocontrol flow of fluid in conduit 62 from inlet 50 to tank 34. Valves92,93 are automatically actuated as will be more fully described.

The filters 70,72 are mounted to the mounting bracket 46. Each of thefilters 70,72 is provided with pressure sensors 94,96 to measurepressure of fluid into the inlets of the filter 70,72 through conduits76,78, respectively, to display the pressure on a main control box 120.

A plurality of fluid level sensors 100-107 are provided within each oftanks 34,36. The plurality includes a dirty fluid overflow level probe100 positioned near a predetermined maximum desired fluid level for tank34. Also disposed within tank 34 is a dirty fluid high level probe 101positioned beneath probe 100. Adjacent the bottom of tank 34 is a firstdirty fluid low level probe 103. Immediately above probe 103 is a seconddirty fluid low level probe 102.

Within clean tank 36 is a clean fluid overflow level probe 104.Positioned beneath probe 104 is a clean fluid high level probe 105.Positioned adjacent the bottom of tank 36 is a first clean fluid lowlevel probe 107. Positioned within tank 36 immediately above probe 107is a second clean fluid low level probe 106. Probes 100-107 arecommercially available probes for detecting fluid levels.

The probes 100-107 are connected to the main control box 120. Also,operating switches for the pumps 66,68 are controlled by control box120. Control box 120 contains control circuitry including control relayshaving activating magnets (referred to herein as relays) controllingswitches. All of such equipment is commercially available and readilyunderstood by one of ordinary skill in the art.

The control circuit of the present invention can best be understood withreference to FIGS. 5 and 6. FIG. 5 is a schematic showing the piping andvalving of the apparatus 20. FIG. 6 is an electrical schematic of thecontrol circuit for the apparatus 20. It will be well understood bythose skilled in the art that preparing a control box 120 having thefunction of the apparatus as herein described and is well within thescope of a person of ordinary skill in the art.

As schematically shown in FIG. 6, the motors of pumps 66 and 68 areelectrically wired across an electrical potential represented byconductors 200,202. Also connected across the potential of conductors200,202 are a plurality of control relays including relays 204-212.

Relays 204,206 control normally open switches 204'-206', respectively.Relay 207 controls normally open switches 207',207a'. Relays 208,209control normally open switches 208',209', respectively. Relay 210'controls normally open switch 210' and normally closed switch 210a'.Relay 211 controls normally open switches 211',211a'. Finally, relay 212controls normally open switches 212',212a'.

A main power manual off/on throw switch 214 is provided to be manuallyactuated to permit operation of pumps 66,68. First solenoid valve 92 isconnected across the potential of lines 200,202 in series with switch206'. Relay 207 is connected in parallel with valve 92 and in serieswith spring biased manual start and stop buttons 215,216.

A timing clock 218 is connected in series with switch 207'. Clock 218and switch 207' are connected in parallel to relay 207 with clock 218cross-connected by conductor 219. Conductor 219 keeps relay 207energized after normally open button 215 is released and until normallyclosed button 216 is pressed.

Switches 207a',210a' and second solenoid valve 93 are connected inseries and, in turn, are connected in parallel to the clock 218 andswitch 207'. The clock 218 is a timer which keeps track of the amount oftime that the clock 218 is energized.

Connected in parallel with switch 210a' and second solenoid valve 93 arerelays 208,209. Relays 210-212 are each connected in series withswitches 208',210',209', respectively.

Relay 206 is connected in series with switches 204',205'. Relays 204,205are each connected across the potential of conductors 200,202. Alsoconnected across the potential of conductors 200,202 are switch 211',motor 66 and switch 211a'. Similarly, switch 212', motor 68 and switch212a' are connected in series.

With reference to both FIGS. 5 and 6, the probes 100-107 act as controlswitches for various relays of FIG. 6. Fluid at probe 100 acts as an"off" switch for relay 204 (i.e., fluid at the level of probe 100 turnsrelay 204 "off"--thereby opening switch 204'--until the fluid level isbelow probe 100 at which point relay 204 is turned "on"--thereby closingswitch 204'). Similarly, fluid at probe 104 acts as an "off" switch forrelay 205 (i.e., fluid at the level of probe 104 turns relay 205"off"--thereby opening switch 205'--until the fluid level is below probe104 at which point relay 205 is turned "on"--thereby closing switch205').

Fluid at probe 101 acts as an "on" switch for relay 210 (i.e., fluid atthe level of probe 101 turns relay 210 "on", thereby closing switch 210'and opening switch 210a'). Once relay 210 is "on", it stays "on" even ifthe fluid level goes below probe 101 until the fluid level goes belowprobe 103. Fluid at probe 103 acts as an "on" switch for relay 208(i.e., the absence of fluid at probe 103 turns relay 208 "off" whichopens switch 208' causing relay 210 to turn "off" thereby opening switch210').

Fluid at probe 105 acts as an "on" switch for relay 209 (i.e., fluid atthe level of probe 105 turns relay 209 "on"--thereby closing switch209'). Relay 209, once turned "on", remains on until fluid level fallsbelow probe 107. The absence of fluid at probe 107 turns relay 209 "off"thereby opening switch 209'. Probes 102,106 act as grounding for probes100,104. It will be appreciated that liquid level probes acting as "on"and "off" switches for relays are well known in the art and form no partof this invention per se.

With the control circuit thus described, the reader will note thatrelays 204,205 are normally energized resulting in normal closure ofswitches 204',205'. As a result, relay 206 is normally energizedresulting in normal closure of switch 206'. Accordingly, as long asliquid level is below probes 100,104, solenoid valve 92 is operated tobe in an open state to permit fluid flow through conduit 60 to becontrolled by second solenoid valve 93. Valve 93 is open as long asliquid is below the level of probe 101.

Upon actuation of the start button 215, relay 207 is actuated causingswitches 207',207a' to close. This initiates the operation of the clock218 to indicate elapsed time of operation until switch 207' is opened.

Closure of switch 207a' energizes the second solenoid valve 93 as longas relay 210 is de-energized resulting in switch 210a' remainingnormally closed. Also, energization of relay 207 permits relays 208,209to become energized thereby closing switches 208',209'. Closure ofswitch 208' energizes relay 210 which closes switch 210'. Closure ofswitch 210' energizes relay 211 and closure of switch 209' energizesrelay 212. Energization of relays 211,212 closes switch pairs 211',211a'and 212',212a', respectively. As a result, pumps 66,68 operate.

In the event liquid level in tank 34 achieves the level of probe 100, anoverflow situation exists and relay 204 is de-energized resulting in theentire system shutting off. Similarly, liquid level attaining probe 104in tank 36 indicates an overflow situation which will open switch 205'and turn off the apparatus 20.

If the liquid level in tank 34 achieves the level of probe 101, relay210 is in an "on" switched position. Therefore, as long as switch 208'is closed, liquid level above probe 101 permits pump 66 to operate. Inthe event the liquid level in tank 34 falls beneath the level of probe103, switch 208' is opened and relay 210 is de-energized resulting inpump 66 being switched off.

In tank 36, if the liquid level rises above probe 105, relay 209 isactivated to close switch 209' and to permit pump motor 68 to operate.Liquid level below probe 107 causes relay 209 to switch "off", to openswitch 209' and to turn "off" pump motor 68.

From the foregoing, the reader will note that if the liquid level withintank 34 rises to the level of probe 101, pump 66 will switch "on" andremain "on" until the liquid level achieves the level of probe 103 atwhich point pump 66 will switch "off" and remain "off" until the liquidlevel returns to the level of probe 101. In the event the level were toachieve the level of probe 100, the entire apparatus 20 will notoperate.

Similarly, in tank 36 if liquid level achieves the level of probe 105,pump 68 will operate until such time as the liquid level achieves thelevel 107 at which time the pump 68 will turn "off" and remain "off"until the liquid level returns to the level 105. In the event the fluidlevel within tank 36 rises above level 104, the entire apparatus 20 willturn "off".

Solenoid valve 92 permits fluid to enter the tank 34 as long as fluidlevels within tanks 34,36 are below the levels of probes 100,104respectively. Valve 93 permits fluid to enter tank 34 as long as fluidlevel in tank 34 is below the level of probe 101 and as long as theoperator has pressed the start button 215.

As a result of the foregoing, the pumps 66,68 act generally independentof one another. Namely, pump 66 is taking dirty fluid from tank 34 andprocessing the fluid through the filters 70,72 into tank 36. Thetransfer operation from tank 34 to tank 36 continues without regard tooperation of pump 68 as long as the fluid level within tanks 34,36 isbeneath the levels of probes 100,104. Also, during operation, tank 34 isreceiving dirty fluid from the HVAC system as long as the fluid levelwithin tanks 34,36 is beneath level of probes 101,104. Pump 68 operateswithout regard to operation of pump 66 as long as the fluid level withintanks 34,36 is beneath the level of probes 100,104.

With the foregoing apparatus, fluid in an HVAC system. can be recycledand cleansed in a batch operation. Tank 34 is constantly filling withdirty fluid which is being cleansed in a batch operation to fillreservoir 36. The cleaned fluid within reservoir 36 is constantly beingpumped back into the HVAC system.

The apparatus 20 includes a control circuitry to prevent accidentaldumping of fluid from the HVAC system. Namely, valves 92,93 and checkvalve 300 prevent uncontrolled discharge of fluid from the HVAC systeminto the apparatus 20.

In operation, the fluid in the HVAC system is cycled repeatedly throughthe apparatus 20. As desired, tank 34 may be drained through valve 54 toremove highly concentrated contaminated fluid which may collect beneaththe level of probe 103. Also, as desired, additives may be added to theHVAC system by admitting such additives to tank 36 through open cover310. Finally, filters 70,72 may be removed and replaced with cleanfilters as desired.

From the foregoing detailed description of the preferred embodiment, ishas been shown how the object of the invention has been attained in apreferred embodiment. However, modifications and equivalents of thedisclosed concepts, such as those which readily occur to one skilled inthe art, are intended to be included within the scope of the claimsattached hereto.

What is claimed is:
 1. A method of cleansing heat transfer liquid in aheating ventilating and air conditioning (HVAC) system, said HVAC systemincluding a pump for circulating said fluid in said system under apressure, said method comprising the steps of:drawing only a portion ofsaid liquid from said system while leaving a remainder of said liquidcirculating within said system by flowing said portion from said systemin response to said pressure and controlling said flow for only saidportion to be drawn from said system; filtering said portion through afilter to provide a cleansed permeate and an uncleansed condensate;delivering said cleansed permeate to said system and returning saiduncleansed condensate for further filtering; drawing a subsequentportion of said liquid from said system while leaving a remainder ofsaid liquid circulating within said system; filtering said subsequentportion through said filter to provide a subsequent cleansed permeateand subsequent uncleansed condensate; delivering said subsequentcleansed permeate to said system and returning said uncleansedcondensate for further filtering; repeatedly drawing still furtherportions and filtering said still further portions through said filterto provide cleansed permeates and repeatedly delivering said cleansedpermeates to said system; whereby said fluid is cleansed in a repeatingbatch process which progressively dilutes uncleansed fluid in saidsystem with cleansed permeate from said filter.